Vehicles, such as passenger cars, usually require a key or a key fob for unlocking the vehicle's doors and for activating the vehicle, e.g. starting the engine. As is well known, such a key may be an electronic remote control key, which unlocks the passenger doors once a user pushes on a key button. It is also known to make use of keyless entry systems for vehicles. With such systems, a vehicle door may for example be unlocked once a user touches a handgrip of the door and also keeps an electronic verification key in the proximity of the door. In the event the electronic key runs out of power, it may further include a physical key for unlocking the vehicle.
Recently, it has also been more common to incorporate a vehicle unlocking function into other devices, such as into smartphones. Thereby, by using for example a so called app (mobile application software) in the smartphone, vehicle doors may be unlocked by running an authentication protocol between the smartphone and the vehicle. However, incorporating physical keys into smartphones for unlocking when the smartphone has no power is not a suitable solution.
Another example of how a vehicle passenger compartment may be unlocked and accessible to a user is to make use of Near Field Communication (NFC) technology. For example, US patent application no. 2016/0358396 A1 discloses to incorporate a passive NFC tag into a mobile device, wherein the passive tag can be used for unlocking a vehicle door or starting the vehicle when for instance the mobile device has run out of battery or is turned off.